Messages in this thread | | | Subject | Re: [PATCH] atm: firestream: Replace GFP_ATOMIC with GFP_KERNEL in fs_send | From | Jia-Ju Bai <> | Date | Fri, 26 Jan 2018 21:56:32 +0800 |
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On 2018/1/26 20:05, Al Viro wrote: > On Fri, Jan 26, 2018 at 04:00:27PM +0800, Jia-Ju Bai wrote: >> After checking all possible call chains to fs_send() here, >> my tool finds that fs_send() is never called in atomic context. >> And this function is assigned to a function pointer "dev->ops->send", >> which is only called by vcc_sendmsg() (net/atm/common.c) >> through vcc->dev->ops->send(), and vcc_sendmsg() calls schedule(), >> it indicates that fs_send() can call functions which may sleep. >> Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL. >> >> This is found by a static analysis tool named DCNS written by myself. > The trouble is, places like > net/atm/raw.c:65: vcc->send = atm_send_aal0; > net/atm/raw.c:74: vcc->send = vcc->dev->ops->send; > net/atm/raw.c:83: vcc->send = vcc->dev->ops->send; > mean extra call chains. It's *not* just vcc_sendmsg(), and e.g. > ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) > ? DROP_PACKET : 1; > bh_unlock_sock(sk_atm(vcc)); > in pppoatm_send() definitely is called under a spinlock. > > Looking through the driver (in advanced bitrot, as usual for drivers/atm), > I'd say that submit_queue() is fucked in head in the "queue full" case. > And judging by the history, had been thus since the original merge...
Thanks for reply :)
I am sorry for this false positive. I think other ATM related patches that I submitted are also false positives, sorry. My tool did not handle this situation of passing function pointer, and I will improve the tool...
Thanks, Jia-Ju Bai
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